(grēb), common name for swimming birds found on or near quiet waters in most parts of the world. Grebes resemble the loon and the duck; they have short wings, vestigial tails, and long, individually webbed toes on feet that are set far back on a short, stubby body. They float lower in the water than do ducks, and at the approach of danger they sink progressively lower and then submerge, a practice which has given them the name helldiver.
They are poor fliers and awkward on land; their loosely constructed nests are either hidden in the rushes and weeds at the water's edge or placed on floating vegetation fastened to growing plants. Many grebes cover their eggs with refuse when they leave the nest, and some carry the young on their backs. They have complex courtship rituals, including dancing in pairs on the water. They eat crustaceans, fish, and aquatic insects and plants; unique among birds is their unexplained habit of swallowing feathers. Grebes were formerly hunted for their silky breast feathers.
The best-known representative in the Western Hemisphere is the pied-billed grebe, Podilymbus podiceps, locally called dabchick, water witch, and didapper. Other grebes are the western and Holboell's grebes of North America and the eared and horned grebes of North America, Europe, Asia, and Africa. There is a flightless species in South America.
Although grebes have been considered to be related to the loon, DNA testing suggests that they may be most closely related to the flamingo. Grebes are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Podicipediformes, family Podicipedidae.